1. Field of the Invention
The present invention relates to an image sensing apparatus such as an electronic still camera and a control method therefor.
2. Description of the Related Art
Conventionally, electronic still cameras and video cameras use a manual focus function which is able to focus on a subject by a photographer's operation of moving a focus lens. In this case, in a case in which an electronic viewfinder is used for focusing, the photographer moves a focus lens to a position considered in focus most, while checking the degree of defocus of an image displayed on the electronic viewfinder. However, it has been difficult for a photographer to carry out focusing precisely while checking an image displayed on the electronic viewfinder, since the electronic viewfinder has a small screen and a low resolution.
In order to solve this problem, a method has been devised for notifying a photographer of the direction of moving a focus lens for focusing. A lens focus state display apparatus disclosed in Japanese Patent Laid-Open No. 6-319073 is intended to automatically detect the gray-scale ratio for a subject in such a way the gray-scale ratio corresponds to the position of a focus lens, and display an indication in such a way the focus lens is moved in a direction in which the gray-scale ratio is increased.
However, in order to obtain the direction of moving the focus lens for focusing with the use of the gray-scale ratio (contrast) for a subject corresponding to the position of the focus lens, it is necessary to obtain the contrast at multiple focus lens positions. As a result, the focus lens will be substantially moved to defocus an image displayed on an electronic viewfinder, resulting poor visual quality. Furthermore, the photographer also feels strangeness, because the degree of defocus of an image on the electronic viewfinder is varied automatically even without operation by the photographer.